A digit is any of the numerals from 0 to 9 used to write numbers. It can also mean a finger or toe, especially in scientific language.
From Latin "digitus" meaning "finger" or "toe," because people once counted using their fingers. Over time, the word shifted to mean the symbols used for counting.
Your fingers and the written digits 0–9 share the same name because fingers were the original calculators. Our whole number system is built around having ten digits on our hands.
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